Manufacture of tetraethyl lead



United States Patent Ofiice 2,907,780 Patented Oct. 6, 1959 2,907,780 MANUFACTURE or TETRAETHYL LEAD William Samuel Melvin, Wilmington, Del., and Arthur Fred Nichols, Woodstown, N.J., assignors to E. I. tlu Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 4, 1955 Serial No. 545,133

2 Claims. (Cl. 260-437) acetone which method avoids uncontrollable rise in temperature, resulting possibly in explosions which could take place should the acetone be added in increased amounts during the early stages of the reaction.

More specifically, the present novel process involves the production of tetraethyl lead from sodium lead alloy and ethyl chloride in the presence of acetone at a temperature within the range of 50100 C.; at least the first half of the reaction is carried out in the presence of not more than 0.002 mole of acetone per mole of NaPb, and then completing said reaction in the presence of an additional 0.002 to 0.04 mole of acetone, said additional acetone being added before thereaction is 90% complete. As a matter of preference, the total acetone utilized is between 0.004 and 0.02 mole per mole of alloy.

It is known that tetraethyl lead may be produced from the reaction of ethyl chloride and sodium lead alloy in the presence of acetone, said acetone being introduced in the ethyl chloride feed. There is a strict limit to the advantage that can be taken of this known method in plant scale operation due to the fact that the initial presence of increased amounts of acetone generates heat very rapidly during the early stages of the reaction and the cooling equipment, which is normally adequate with a large factor of safety to maintain the reaction at a constant temperature, cannot handle the greatly increased load. An uncontrolled increase in temperature would result from a substantial increase in the amount of acetone initially added and would thus possibly lead to a disastrous explosion or loss of the charge and a serious contamination problem. Accordingly, the proportion of acetone which can be safely used according to known methods and plant operation has been strictly limited. Under known methods, approximately 0.08% by weight of acetone in the ethyl chloride is utilized; a concentration of acetone in said ethyl chloride of 0.13% by weight or more in the early stages of the reaction would definitely be unsafe. These figures apply to the normal plant equipment and present end normal size of charge and ratio of alloy to ethyl chloride in the production of tetraethyl lead. It is noted that more acetone could be used safely at the start of the process if greater cooling were applied or if more ethyl chloride were used. However, these changes would involve more costly equipment and result in a serious decrease in tetraethyl lead capacity since less were increased.

alloy could be used as charge if the ratio of ethyl chloride The present invention is carried out in regular plant equipment and according to the general procedure which has been used for a number of years in making tetraethyl lead by batch operation. It has been found that the yield of tetraethyl lead obtained in a given time corresponding to the practical reaction cycle may be unexpectedly increased with complete safety by the use of increased quantity of acetone introduced according to the spirit of this process which introduces predetermined amounts of acetone into the feed tank for mixing with predetermined amounts of ethyl chloride; no special equipment is required.

The following examples are illustrative of the present invention:

Example 1 An autoclave used for making TEL was charged with 3500 lbs. of ground NaPb alloy and 1500 lbs. of liquid ethyl chloride was fed in over about 30 minutes, the pressure being kept at about lbs. per sq. in. gauge'pressure and the temperature being between '78 and 84 C. The ethyl chloride contained 0.08% or 1.2 lbs. of acetone, a concentration which it has been found safe to use in large scale ethylations. This amount of acetone corresponds to 0.00136 mol per mol of NaPb present. Determination of the heat evolved showed that the ethylation of the alloy was 66% complete at the end of the addition of this first portion of ethyl chloride. A second addition of ethyl chloride was then made, consisting of 200 lbs. containing 2.96 lbs. of acetone, corresponding to an additional 2.8 lbs. of acetone, or 0.003 mol per mol of NaPb, plus the amount of acetone, 0.16 lb. (0.00018 mol per mol of alloy) which would have been added if a 0.08% solution had been used as in the first addition of ethyl chloride. The addition of this second portion of ethyl chloride occupied about 5 minutes, the pressure being maintained as before. The last portion of ethyl chloride was then added, consisting of 500 lbs. containing 0.40 lb., 0.00045 mol per mol of alloy, or 0.08% of acetone, and the reaction was continued to give a total of 2 hours and 10 minutes reaction time. Throughout the run, there was no tendency for the temperature to rise uncontrollably. The charge was then worked up in the usual way by venting off the unused ethyl chloride and removing the TEL by steam distillation. The yield was 90.49%, based on the alloy charged. It will be seen that this schedule for the addition of ethyl chloride and acetone gives a total of 0.005 mol of acetone per mol of alloy, only 0.00136 mol of which was added during the main part of the reaction, the res-t, 0.00364 mol, being added after 66% of TEL was formed.

In a similar run, except that no extra acetone was added, that is, a total of 0.002 mol was added as a 0.08% solution in the total ethyl chloride used, as in known plant procedure, the yield was only 88.94%.

Example 2 The procedure of Example 1 was followed, except that the second addition of ethyl chloride, 2 00 'lbs., contained 16 lbs. of acetone. This gives a total of 0.02 mol of acetone per mol of alloy. The yield was 90.65%.

Example 3 Example 4 The procedure of Example 3 was followed except as follows. The first addition of ethyl chloride, containing only 0.0009 mol of acetone per mol of alloy, was 1000 lbs. and required 45 minutes. The reaction was 55% complete after this first addition and before the addition of 16.56 lbs. of acetone in 700 lbs. of ethyl chloride. Thetotal acetone was 0.02 mol per mol of alloy. A final addition of 500 lbs. of ethyl chloride containing 0.08% acetone was made to bring the total ethyl chloride to 2200 lbs. The yield was 89.03%, compared with 37.29% in the absence of the additional acetone.

- In carrying out the present invention, many deviations from the specific conditions described in the above examples are permitted provided that the conditions which :form the basis for the claimed invention are adhered to. Thus, the additional acetone may be added at any time after the reaction is half completed and before it is 90% completed and may be added either gradually over this period or rapidly during any part of the period, or by a combination of these, as shown in the above examples. However, it is best to add the acetone considerably diluted with ethyl chloride. The addition of ethyl chloride may be stopped at any time after the required amount of acetone has been added. The ratio of ethyl chloride to alloy may be varied widely, depending on considerations already discussed in publications on tetraethyl lead. The weight of ethyl chloride should, however, be more than that theoretically required to react with all the alloy and need not in general be more than about four times the weight of the alloy. The theoretical quantity of ethyl chloride reacting with 100 parts by weight of alloy is 28 (i.e., is an equimolar quantity). The examples above set forth utilizes 63 parts ethyl chloride. batch process not more than 100 parts will be used.

We claim: I

1. In the manufacture of tetraethyllead from sodium lead alloy and ethyl chloride in the presence of acetone at a temperature within the range of50 to 100 C., wherein acetone and ethyl chloride are fed to said alloy in such proportions that (a) the quantity of acetone being fed to the reactor is less than 0.13% by weight of the ethyl chloride being fed to the reactor, and, (b) the total quantity of acetone added to the reactor corresponds to not more than about 0.002 mole of acetone per mole of alloy based on the total original quantity of said alloy, the improvement which comprises increasing said proportion of acetone in the feed to greater than 0.13% of the ethyl chloride'when at least 50% and'before of said alloy has been ethyllated to result in the presence of an additional 0.002 to 0.04 mole of acetoneper mole of alloy, based on the original quantity of said alloy, in the reactor.

2. The process of claim 1 wherein the total amount of acetone present is between 0.004 and 0.02 mole per mole of sodium lead alloy.

References Cited in the file of this patent UNITED STATES PATENTS 2,464,397 Holbrook Mar. 15, 1949 Ordinarily in a 

1. IN THE MANUFACTURE OF TETRAETHYLLEAD FROM SODIUM LEAD ALLOY AND ETHYL CHLORIDE IN THE PRESENCE OF ACETONE AT A TEMPERATURE WITHIN THE RANGE OF 50 TO 100*C., WHERE IN ACETONE AND ETHYOL CHLORIDE ARE FED TO SAID ALLOY IN SUCH PROPORTIONS THAT (A) TEH QUANTITY OF ACETONE BEING FED TO THE REACTOR IS LESS THAN 0.13% BY WEIGHT OF THE ETHYL CHLORIDE BEING FED TO THE REACTOR, AND, (B) THE TOTAL QUANTITY OF ACETONE ADDED TO THE REACTOR CORRESPONDS TO NOT MORE THAN ABOUT 0.002 MOLE OF ACETONE PER MOLE OF ALLOY BASED ON THE TOTAL ORIGINAL QUANTITY OF SAID ALLOY, THE IM PROVEMENT WHICH COMPRISES INCREASING SAID PROPORTION OF ACETONE IN THE FEED TO GREATER THAN 0.13% OF THE ETHYL CHLORIDE WHEN AT LEAST 50% AND BEFOR 90% OF SAID ALLOY HAS BEEN ETHYLLATED TO RESULT IN THE PRESENCE OF AN ADDITIONAL 0.002 TO 0.04 MOLE OF ACETONE PER MOLE OF ALLOY, BASED ON THE ORIGINAL QUANTITY OF SAID ALLOY, IN THE REACTOR. 